Low Dose Niacin (Vitamin B3) for Parkinson's Disease

Inclusion Criteria: * PD subjects will be adult men and women diagnosed with idiopathic mild to moderately severe PD * The majority of PD subjects are expected to be \> 60 years old * Disease severity is defined as modified Hoehn \& Yahr Stages I-IV (while "On") * PD is defined according to the UK Brain Bank Criteria made at least six months prior to recruitment to the study * PD features include the presence of at least two of the four cardinal clinical manifestations of the disease, which are: * tremor * rigidity * bradykinesia * disturbances of posture or gait, without any other known or suspected cause of Parkinsonism * Subjects should be stabilized on PD medication for at least 3 months before enrollment into the study * Subjects' PD drug prescriptions will not be altered nor withheld during the study * The patient will have signed informed consent Exclusion Criteria: * Subjects will be excluded if they present with significant cognitive deficits * A MMSE score of 25 is considered substantial global cognitive impairment * Subjects will be excluded if they had previous brain surgery or other severe neurological problems * intracerebral hemorrhage * traumatic brain injury * central nervous system malignancy * active central nervous system (CNS) infection * significant stroke * Alzheimer disease or any type of implanted stimulator including but not limited to Deep Brain Stimulator (DBS) or pacemaker * All subjects must be without evidence of dementia * defined as a score \> 24 the Mini-Mental State Examination and able to understand test instructions * Subjects must not have functional blindness (inability to participate in gait and visuomotor assessments) or lower limb amputation higher than the forefoot or any orthopedic problem that precludes performance of physical tests * Subjects must not have known allergy to vitamin B3 * Significant cardiac, pulmonary, hepatic, gastrointestinal, renal disease, or uncontrolled/advanced diabetes are also exclusionary factors, e.g.: * New York Heart Association Class III or IV congestive heart failure * endocarditis * pulmonary insufficiency symptomatic at rest or with mild physical exertion * acute or chronic hepatitis * renal failure requiring dialysis * second and third degree atrioventricular (AV) block * sick sinus syndrome * Subjects will be excluded if they are taking B3 but will be included if they are taking B complex that has very low dose B3 (25 mg) which has minimal effects on GPR109A (based on our unpublished observation) * Overall, the investigators will exercise clinical judgment to exclude a subject from the study if, in the investigators' opinion, that a patient presents with a set of comorbidities which renders unsuitability for the study